AWS Certified Developer Exam Notes – Cloudformation

Posted on by antonogeo

CloudFormation

  • Infrastructure as code. Free.
  • You can schedule the destruction and re-creation of the environment 
  • The templates have to be uploaded in S3
  • You can’t edit the current version, we need to re-upload a new version.
  • When you upload a new template, you can see the changes in Change Sets. 
  • Cloudformation knows the right order for resource creation.
  • Rollbacks
    • If the update fails, the service is automatically rolled back to the previous working state.
    • You need to enable it in stack creation options

Cloudformation Drift Detection

  • Detects changes that happened manually on the resources!
  • Stack actions -> Detect drift

Stacks

  • You create Stacks. They contain Events (creation events), Resources, Templates etc
  • Nested stacks are stacks contained in other stacks.
  • To create a nested stack, specify the AWS::CloudFormation::Stack
  • StackSets help you update infrastructure in different regions and Accounts.

Components

  • Resources – Mandatory
  • Parameters
  • Mappings
  • Outputs
  • Conditionals
  • Metadata

Parameters

  • Define them in the Parameters section
  • Use them with !Ref. This can be used to reference parameters or resources.
  • Pseudo Parameters: Some default parameters like AWS::AccountId etc

Mappings

  • Hard-Coded variables 
  • Matches a key to a corresponding set of named values
  • !FindInMap [MapName, TopLevelKey, SecondLevelKey]

Outputs

  • You can export output and import it into another stack
  • You cannot delete a stack if it has referenced output to other stacks
  • Export: to export it and !ImportValue to import an output

Conditions

  • !Equals [!Ref ParameterName, value]
  • Used by the Condition: ConditionName

 

Intrinsic Functions

  • !Ref – Reference parameters of resources. Returns the resources ids
  • !GetAtt. Get parameter attributes. Unlike Ref, this can return any attribute of the resource, not only the id. Example: !GetAtt EC2Instance.AvailabilityZone
  • !FindInMap[ MapName, TopLevelKey, SecondLevelKey ] – Return Mapping value
  • !ImportValue – Import value that has been exported
  • !Join – Joins a comma-separated list with “:”
  • !Sub – Substitute values in strings
  • Conditions – And , Equals, If, Not , Or